The present invention relates to a technique of boosting the voltage value of power being supplied and outputting the boosted power.
Terminals accorded to the USB (Universal Serial Bus) standard have been widely spread in personal computers etc. Various kinds of peripheral devices can be coupled via the USB terminal. Since such a USB terminal includes a signal line and a power supply line, the peripheral device coupled to the USB terminal can be supplied with power from the power supply line. The power supply line is restricted in its allowable voltage to be 5 volt or less and in its allowable current to be 500 mA or less due to the standard of the USB terminal, so that the usable power is 2.5 W at the maximum.
However, in some of the peripheral devices to be coupled to the USB terminals, a consumption power instantaneously exceeds 2.5 W at the peak. Thus, as disclosed in JP-T-2004-503199, there has been proposed an apparatus in which a capacitor is provided at an input portion for receiving power from the power supply line of the USB terminal, and a power at the peak time of the peripheral device coupled to the USB terminal is compensated by utilizing power accumulated in the capacitor.
However, since the apparatus disclosed in JP-T-2004-503199 is configured to merely employ the capacitor, there arises a problem that a power capable of being accumulated is small. Further, since it is necessary to greatly increase the capacity of the capacitor in order to increase the accumulated power, the volume of the capacitor becomes quite large. Thus, in a case of a USB amplifier for driving a speaker, since a capacitor of a large capacity is required, the amplifier can not be miniaturized.